As discussed under 1 Nephi 17:32, the original text has examples of a mixed gerundive construction. Here in Alma 17:14, the original text has the definite article the but not the expected preposition of after murdering. In his editing for the 1837 edition, Joseph Smith deleted the the, thus making “murdering the Nephites” conform to the following conjoined “and robbing and plundering them”. The critical text will restore the original usage despite its difficulty. For a general discussion, see under gerundives in volume 3.
Summary: Restore in Alma 17:14 the definite article the in the original mixed gerundive construction “a people which delighted in the murdering the Nephites”; this usage, although unexpected in modern English, is found quite frequently in the original Book of Mormon text.